1. Field of the Invention
The present invention relates to an apparatus for determining the exposure conditions in, for example, a photolithography step included in a manufacturing process of a semiconductor device, a method of determining the exposure conditions, and a process apparatus equipped with the apparatus for determining the exposure conditions.
2. Description of the Related Art
In, for example, the photolithography step included in a manufacturing process of a semiconductor device, a resist film is formed first on the surface of a semiconductor wafer, followed by subjecting the wafer to an exposure treatment in which the resist film is selectively exposed to light in a predetermined pattern and subsequently subjecting the exposed wafer to a developing treatment so as to form a predetermined pattern on the wafer.
Prior to the exposure treatment, performed is an operation called the operation for determining the exposure conditions for setting the exposure amount and the focus value at optimum values. The operation for determining the exposure conditions is performed because the conditions of the exposure apparatus such as the intensity and stability of the light source and length of the optical path are slightly changed, with the result that developed patterns having the identical shape accuracy is not always formed on the wafer even if the set values on the operating panel of the exposure apparatus are set constant. It follows that the operation for determining the exposure conditions is indispensable for forming a predetermined pattern on the article and, thus, the particular operation is performed periodically, e.g., at an interval of one week or one day.
In general, the operation for determining the exposure conditions is carried out as follows. Specifically, in the first step, a single wafer having a resist film formed thereon is selectively exposed to light in a predetermined pattern using a mask (reticle) having a predetermined pattern formed therein with, for example, the exposure amount changed in the column direction and with the focus value changed in the row direction. Then, the exposed wafer is subjected to a baking treatment, followed by further applying a developing treatment to the wafer. Further, the developed pattern thus obtained is observed with, for example, a scanning electron microscope (SEM). The exposure conditions giving the best developed pattern are determined on the basis of the result of the microscopic observation.
However, in the operation for determining the exposure conditions in which the line width of the fine pattern of the mask or the wafer is measured by a length measuring SEM, the operator is required to be sufficiently skilled in the operation of the length measuring SEM. Also, the time required for the judgment of the measured values differs depending on the operator. Such being the situation, a long time is required for determining the optimum exposure conditions so as to make it difficult to improve the production efficiency. The improvement in the production efficiency is also inhibited in the case where the selective judgment of the optimum exposure conditions differs depending on the operator and, thus, the exposure conditions are changed every time the exposure treatment is carried out.
It should also be noted that, in recent years, the exposure treatment is rendered complex so as to increase the number of steps of the operation for determining the exposure conditions, with the result that a long time is required for the operation for determining the exposure conditions. Under the circumstances, it is required to shorten the time for determining the exposure conditions. Further, in order to maintain a high quality of the article and to improve the product yield by finding promptly the disorder of the exposure apparatus and the change in the conditions, it is desirable to confirm on the real time basis whether the developed pattern obtained in the photolithography step has a predetermined shape accuracy.
An object of the present invention is to provide a an apparatus for determining the exposure conditions, which permits improving the production efficiency by automating the operation to determine the exposure conditions so as to decrease the number of process steps and also permits maintaining the quality of the product, a method for determining the exposure conditions, and a process apparatus equipped with the apparatus for determining the exposure conditions.
According to a first aspect of the present invention, there is provided an apparatus for determining the exposure conditions in the lithography step, comprising means for converting a developed pattern into an optical information formed by exposing a plurality of different positions of a substrate at different exposure amounts and focus values to light at a predetermined pattern and developing said pattern and for determining an optimum combination of the exposure amount and the focus value based on said optical information.
According to a second aspect of the present invention, there is provided an apparatus for determining the exposure conditions, in which the operation to determine the exposure conditions is performed by using a substrate being exposed in a plurality of different positions thereof at different exposure amounts and focus values to light at a predetermined pattern by using a mask having said predetermined pattern formed therein, and, then, being developed, comprising a light irradiating section for irradiating a predetermined range of the developed pattern formed on the substrate with light having a predetermined intensity; a detecting section for detecting the optical information of a predetermined region within said predetermined range; and an arithmetic process section for searching the position where the exposure treatment has been applied under an optimum exposure amount and focus value from said optical information thereby to determine the optimum exposure conditions.
According to a third aspect of the present invention, there is provided a method for determining the exposure conditions in the photolithography step, comprising a first step of exposing a plurality of different positions of a substrate at different exposure amounts and focus values to light at a predetermined pattern; a second step of converting the state of the developed pattern formed by developing said substrate into an optical information; and a third step of determining an optimum combination of the exposure amount and the focus value based on said optical information.
According to a fourth aspect of the present invention, there is provided a method for determining the exposure conditions in the photolithography step, comprising a first step of exposing a plurality of different positions of a substrate at different exposure amounts and focus values to light at a predetermined pattern by using a mask having said predetermined pattern formed therein; a second step of forming a developed pattern by developing the substrate; a third step of irradiating a predetermined range of said developed pattern with light having a predetermined intensity thereby to measure the optical information on the light reflected from irradiated portion; and a fourth step of comparing said optical information with reference data prepared in advance and including information obtained by the visual observation and optical information thereby to determine the optimum light exposure amount and the optimum focus value from the combinations of the light exposure amounts and the focus values employed in said first step.
According to a fifth aspect of the present invention, there is provided a method for determining the exposure conditions in the photolithography step, comprising a preparatory process and a main process,
wherein said preparatory process includes a first preparatory step of exposing a plurality of different positions of a substrate at different exposure amounts and focus values to light at a predetermined pattern by using a mask having said predetermined pattern formed therein; a second preparatory step of forming a reference developed pattern by developing the substrate; a third preparatory step of observing said reference developed pattern with an SEM thereby to obtain information on the shape of said reference developed pattern; a fourth preparatory step of irradiating a predetermined range of said reference developed pattern with light having a predetermined intensity thereby to obtain information on the reflected light; and a fifth preparatory step of preparing reference data in which said information on the shape is correlated with the optical information obtained in said fourth preparatory step, and
said main process includes a first step of forming a predetermined developed pattern on a substrate in accordance with the process similar to that in said first preparatory step and said second preparatory step; a second step of irradiating a predetermined range of said developed pattern with light having a predetermined intensity thereby to measure the optical information on the reflected light; and a third step of comparing said optical information with said reference data thereby to determine the optimum exposure amount and the optimum focus value from the combinations of the exposure amounts and the focus values employed in said first step.
According to a sixth aspect of the present invention, there is provided a process apparatus including a developing process section for applying a developing treatment to a substrate subjected to a exposure treatment, comprising an apparatus for determining the exposure conditions, in which a developed pattern is converted into an optical information formed by exposing a plurality of different positions of a substrate at different exposure amounts and focus values to light at a predetermined pattern and developing said pattern in said developing process section thereby to determine the optimum exposure amount and the optimum focus value based on said optical information.
According to a seventh aspect of the present invention, there is provided a process apparatus including a developing process section for applying a developing treatment to a substrate subjected to a exposure treatment, said process apparatus comprising an apparatus for determining the exposure conditions, in which the operation to determine the exposure conditions is performed by using a substrate being exposed in a plurality of different positions thereof at different exposure amounts and focus values to light at predetermined pattern by using a mask having said predetermined pattern formed therein, and, then, being developed in said developing process section, wherein said apparatus for determining the exposure conditions includes a light irradiating section for irradiating a predetermined range of said developed pattern formed on the substrate with light having a predetermined intensity; a detecting section for detecting the optical information of a predetermined region within said predetermined range; and an arithmetic process section for searching the position where the exposure treatment has been applied under the optimum exposure amount and the optimum focus value from said optical information thereby to determine the optimum exposure conditions.
According to an eighth aspect of the present invention, there is provided a process apparatus comprising a resist coating process section for forming a resist film on a substrate; a exposure apparatus for applying a exposure treatment to the substrate having said resist film formed thereon; a developing process section for applying a developing treatment to the substrate subjected to the exposure treatment by using said exposure apparatus; and an apparatus for determining the exposure conditions, in which a developed pattern into an optical information formed by exposing a plurality of different positions of a substrate at different exposure amounts and focus values to light at a predetermined pattern by using said exposure apparatus and the developing said pattern in said developing process section and for determining an optimum exposure amount and an optimum focus value based on said optical information and to feed back said optimum exposure amount and said optimum focus value to said exposure apparatus.
According to a ninth aspect of the present invention, there is provided a process apparatus comprising a resist coating process section for forming a resist film on a substrate; a developing process section for applying a developing treatment to the substrate subjected to the exposure treatment; and an apparatus for determining the exposure conditions, in which a developed pattern is converted into an optical information formed by exposing a plurality of different positions of the substrate having the resist film formed thereon at different exposure amounts and focus values to light at a predetermined pattern and developing said pattern in said developing process section thereby to determine the optimum exposure amount and the optimum focus value from said optical information.
According to a tenth aspect of the present invention, there is provided a process apparatus comprising a resist coating process section for forming a resist film on a substrate; a developing process section for applying a developing treatment to the substrate subjected to the exposure treatment; an optical information detecting section for detecting a developed pattern as an optical information formed by exposing a plurality of different positions of the substrate having a resist film formed thereon at different exposure amounts and focus values to light at a predetermined pattern and developing said pattern in said developing process section; and a coating-developing control section for determining the process conditions in said resist coating section and/or said developing process section from the optical information detected by said optical information detecting apparatus thereby to feed back said determined process conditions to said resist coating process section and/or said developing process section.
According to the present invention, the operation to determine the exposure conditions, which was performed in the past by the judgment of an operator on the basis of the result of the SEM observation, can be automatically performed by using an optical information such as the reflected light intensity, making it possible to decrease the number of process steps so as to improve the production efficiency. Also, it is possible perform easily the checking of the exposure conditions at a predetermined timing, e.g., at an interval of several hours, in addition to the operation to determine the exposure conditions performed every day or every week in the past, so as to make it possible to maintain a high quality of the product. It should also be noted that, when the optical information obtained in the operation to determine the exposure conditions is far apart from the reference date measured in advance, it is suggested that disorder has taken place in light exposure apparatus, the resist coating-developing process system performing a series of operations, and the apparatus for determining the exposure conditions. Therefore, it is possible to detect the disorder of these apparatuses in an early stage from the optical information so as to cope with the disorder.
It is possible to arrange the apparatus for determining the exposure conditions having above constitution in the box in which the process section for performing the resist coating and the developing treatment is arranged or within the exposure apparatus, making it possible to monitor the formed state of the developed pattern on the real time basis in parallel to the resist coating treatment, etc. It follows that it is possible to maintain a high quality of the product. It should also be noted that, if the apparatus for determining the exposure conditions is constructed such that an alarm is emitted in the case where the difference between the detected optical information and the reference data is large, it is possible to obtain an additional effect that the number of substrates that are rendered useless is decreased.